Acute vitamin D2 (ergocalciferol) toxicosis in horses: case report and experimental studies.

This research paper investigates the impact of acute (sudden) vitamin D2 (ergocalciferol) toxicosis in horses, including case studies and rate experiments among horses of various weights and ages over a 21-day period.

Experiment Details

The research experiment involved four horses, one of which was a 6-month-old foal diagnosed with extensive soft tissue mineralization due to accidental overdose of Vitamin D2 (ergocalciferol). The three remaining horses, all 18-month-olds, were administered with different doses of ergocalciferol. These doses were respectively 9,300 IU/kg, 22,200 IU/kg, and 47,200 IU/kg of horse body weight per day for 21 days.

Oberservations and Findings

• The researchers tracked signs and symptoms in the horses and found that the animals given smaller and intermediate doses showed neither clinical signs nor lesions. However, the horse given the highest dose developed symptoms similar to the foal’s, reflecting impacts of ergocalciferol intoxication.
• In both the foal and the horse given the highest dose, gross and histologic lesions of mineralization in various soft tissues were observed, especially in the endocardium and the large blood vessel walls.
• Notably, the symptomatology included depression, loss of appetite, weakness, limb stiffness with impaired mobility, and cessation of growth or weight loss. These were seen in the 6-month-old foal and the horse given the high dose of ergocalciferol.
• Among the tested horses, each developed marked, persistent, hyperphosphatemia, with phosphorus serum levels ranging from 7.0 to 13.0 mg of P/dl of serum.
• Calcium levels varied among the horses, with those given the low and high doses becoming hypercalcemic but returning to normal calcium levels by the end of the study. The horse given the intermediate dose maintained normal calcium levels throughout.
• Magnesium levels in serum or distal metacarpal bone ash concentrations weren’t significantly affected by ergocalciferol treatment.

Conclusions

Based on the findings, the study concludes that overdose of ergocalciferol can lead to serious symptoms such as depression, loss of appetite, weakness, limb stiffness with impaired mobility, and halted growth or weight loss. Exceptionally high doses may also cause mineralization in various soft tissues. The research will help in diagnosing and managing ergocalciferol toxicity in horses and other similar animals.